There are 166 estuaries in Western Australia as established through the National Land and Water Resources Audit (NLWRA) 2000, where an estuary is defined as a semi-enclosed body of water where fresh water and sea water mix. Estuaries could also be considered as the mixing zone where rivers meet the sea - it is important to note that this mixing zone could extend many kilometres inland from the coast.
The majority of WA estuaries lie in the Kimberley and are considered by the NLWRA as tidal dominated estuaries given the high tidal fluctuations. These estuaries are in the main considered near pristine since the estuaries are relatively unmodified apart from extensive pastoral development in the catchments.
Along the arid Pilbara and subtropical west coast the rivers rarely run to the sea and the river mouths are mostly marine.
The most affected and changed estuaries are the 40 that lie in the greater South West extending from the Murchison River at Kalbarri to Barker Inlet west of Esperance. From a management perspective we further divide the greater South West into the: Mid West extending from the Murchison River to the Moore River at Guilderton; South West extending from the Swan-Canning to the Hardy Inlet at Augusta, and the South Coast extending from Donnelly River to Barker Inlet near Esperance. These are denoted as wave dominated estuaries by the NLWRA.
Moore River estuary